1. Field of the Invention
The invention relates in general to a touch control system, and more particularly, to a correction technology of a touch control system including multiple sensing regions.
2. Description of the Related Art
Operating interfaces of recent electronic products have become increasingly user-friendly and intuitive with the progressing technology. For example, through a touch screen, a user can directly interact with applications and input messages/texts/patterns with fingers or a stylus, thus eliminating complexities associated with other input devices such as a keyboard or buttons. In practice, a touch screen usually comprises a touch panel and a display disposed at the back of the touch panel. According to a touch position on the touch panel and a currently displayed image on the display, an electronic device determines an intention of the touch to execute corresponding operations.
Existing capacitive touch sensing techniques can be roughly categorized into self-capacitive and mutual-capacitive types. Compared to mutual-capacitive touch panels, self-capacitive touch panels can be implemented through a single-layer electrode with a simpler manufacturing process and lower costs, and thus prevail in many entry-level electronic products. FIG. 1 is an exemplary electrode configuration of a self-capacitive touch panel. A sensing region 100 represented by a dotted frame includes a plurality of triangular electrodes in a staggered arrangement along the X direction. The electrodes are connected to one or multiple sensors (only a first sensor 13 connected to an electrode 11 and a first sensor 14 connected to an electrode 12 are depicted as an example), which then detect capacitance changes of the electrodes. The detection results are provided to a controller (not shown) for the controller to determine a position of the user touch.
To increase a touch control area, an electrode configuration that forms multiple sensing regions is developed in the recent years. In the example in FIG. 2, electrodes are divided into an upper group and a lower group to respectively form two different sensing regions 210 and 220. In current technologies, a controller determines a Y coordinate Y0 of the touch point according to an equation below:
                              Y          0                =                                            Ucd                              (                                  Ucd                  +                  Dcd                                )                                      ×                          y              1                                +                                    Dcd                              (                                  Ucd                  +                  Dcd                                )                                      ×                          y              2                                                          equation        ⁢                                  ⁢                  (          1          )                    
In equation (1), Ucd represents a total capacitance change of all the electrodes in the sensing region 210, Dcd represents a total capacitance change of all the electrodes in the sensing region 220, yi represents a Y coordinate according to only the capacitance changes in the sensing region 210 (i.e., the capacitance changes in the sensing region 220 are not considered), and y2 represents a Y coordinate calculated according to the capacitance changes in the sensing region 220 (i.e., the capacitance changes in the sensing region 210 are not considered).
Referring to FIG. 3, when a touch position occurs at a position 30A, it mainly affects the sensing region 210, and so a noticeable total capacitance change UcdA occurs. At this point, a total capacitance change DcdA is almost zero. When the value of the total capacitance change DcdA is lower than a threshold, the total capacitance change DcdA may be omitted when the coordinate Y0 is calculated. In this situation, the coordinate Y0 is equal to the coordinate y1. In contrast, when the position of the user touch occurs at a position 30B, the influence of the touch event is quite evenly distributed to the two total capacitance changes UcdB and DcdB. It is apparent that values of both the total capacitance changes UcdB and DcdB are lower than the total capacitance change UcdA. For example, the value of the total capacitance change UcdA may be around 500 microfarad (μF), and the values of the total capacitance changes UcdB and DcdB may be around 200 Known to one person skilled in the art, compared to the total capacitance change UcdA, signal-to-noise (SNR) ratios of the total capacitance changes UcdB and DcdB are lower. As seen from equation (1), when the total capacitance changes UcdB and DcdB are considered (i.e., when the user touch occurs at an intersection region of the sensing regions 210 and 220), the noises in the total capacitance changes UcdB and DcdB impose considerable effects on the calculation result. More specifically, as a drawback of a conventional solution, when the user touch occurs at an intersection region of the sensing regions 210 and 220, the coordinate Y0 calculated according to equation (1) usually contains a large error. Such situation of an error occurring at a boundary region of the sensing regions may lead the controller to misjudge a user intention to further cause an erroneous operation result.